Planet Earth II

In northern India, tha tallest grasses in the world can hide animals even as tall as elephants. A herd of Asian elephants here moves through the dense growth, browsing as they go.

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Saiga antelope inhabit the largest grassland on the planet, the Eurasian Steppe. Females typically give birth to twins to coincide with spring rains and the fresh growth of grass that follows. The grass provides not only a source of food but also cover; whilst lying down, the babies are hidden from predators. Saiga are nomads and undertake long migrations, using their oddly-shaped noses to detect fresh growth hundreds of kilometres away.

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For a pride of lions in Botswana, the annual flooding of the Okavango Delta makes it harder to run down prey. With three-mongh-old cubs to feed, their mothers must make a kill soon. The transformation of the delta into a watery grassland does attract new, slower moving prey such as African buffalo. Five lionesses attempt to take down a single large bull. One female distracts the bull up front, while the others try to topple him from behind; this is easier said than done as the lions have very little traction on the swampy ground. This time, the bull escapes and the pride must try again.

African buffalo arrive at the Okavango Delta in herds 2,000 strong, driven by the fresh growth of grass amid the annual flooding. Predators such as lions pose little danger to the largest bulls. One such bull faces a team of five lionesses but, after a lengthy struggle, he manages to shake them off and escapes, wounded but alive, and thanks to his endurance and thick hide.

Flowering European meadows represent a lush opportunity for harvest mice, which are adept at climbing through the grasses to find food. One female, a mother with babies to feed, does so expertly, using her prehensile tail to wrap around stems for balance as she manoeuvres the vegetation, as well as to free up her hands to feed. Heading up the "canopy" to find the best foods exposes her to predators such as barn owls in the skies above. Though harvest mice seldom venture all the way to ground level, they are able to navigate their way back to their nests by reading the pattern of stems overhead.

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Barn owls hunt rodents, such as harvest mice, which inhabit grasslands. An owl hovers over a spot in a meadow that appears to conceal prey and takes a dive, but its quarry escapes.

Carmine bee-eaters are excellent aerial hunters, being able to manoeuvre in the air to snap up flying insects. However, their prey tends to stay within the safety of the savannah grasses when alarmed. The bee-eaters make use of a wide range of large, bulky host animals, including kori bustards, ostriches and elephants. As they move through the grass, they inadvertantly flush out insects into the air, where the bee-eaters pick them off. Elephants in particular are preferred because they are so large, they hardly notice the bee-eaters.

As the world's largest flying bird, the kori bustard is an attractive perch for carmine bee-eaters looking pick off insects from the grass.

As the world's largest and heaviest bird, ostriches are an attractive perch for carmine bee-eaters looking pick off insects from the grass. However, these uninvited passengers will only be tolerated for so long - eventually the ostriches brush the bee-eaters off their backs with a swing of their wings.

No other animal on the savannah comes close to the African bush elephant in size. This makes them the ideal hosts for commensalist carmine bee-eaters, which hover close to the front of the animal's tusks as it walks and in doing so flushes out insects from the grass that the bee-eaters gorge on.

The serval has the longest legs and the largest ears of any cat relative to its body size. These features enable it to stalk thick grasslands, its legs affording it a better vantage point above the tops of the stems, and its ears helping to pinpoint a moving target. A hunting female picks up the rustle of a vlei rat in the grasses and leaps into the air to pounce. Despite several attempts, she comes up empty-handed. When prey is more abundant, servals are able to catch prey up to 70 times a day.

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Southern African vlei rats hiding in thick grass are prey for animals such as servals. To evade detection, they remain as still as possible and move in short bursts.

Over 2 million wildebeest follow a nomadic way of life in East Africa's savannahs in pursuit of fresh grazing.

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Male Jackson's widowbirds have to go to great lengths to attract a mate on the tall grasses of East Africa's savannahs. In the mating season, males adopt a long downcurved tail as part of their breeding plumage. They first set up a courtship arena, trimming blades of grass to length, to clear a space. Then, they begin to jump vertically up so as to rise above the height of the grasses and attract of the attention of nearby females. Those males that are able to rise the heighest and continue doing so for the longest win the most mates. Once a female arrives, the male begins his courtship ritual, puffing his feathers and following around the female as she explores his arena.

Blades of grass that are too tough for larger grazers pose no challenge to grass-cutter ants such as the Chacho leafcutter ant. These ants harvest grass on an industrial scale in order to feed fungus that grows in their nests. As the fungus feeds the rotting grass, it in turn feeds the ants. A single colony can collect over half a tonne of grass annually.

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Termites are able to break down dead grass to extract nutrients. On the Cerrado, termite mounds are susceptible to attack by giant anteaters. Here, wildfires also pose a danger; they can turn grasslands to ashes within minutes but the resilience of grasses means that, in time, they will sprout again to once again serve as a food source for the termites.

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Giant anteaters can eat 20,000 insects a day. It uses its half-metre-long tounge, which is covered in microscopic hooks, to reach deep into termite hills in order to extract its food. It's also armed with powerful forelimbs and long claws that allow it to demolish these hills with ease. In the Cerrado, wildfires can turn grasslands to ashes within minutes but the resilience of grasses means that, in time, they will sprout again. In this way, the ecosystem, including this particular predator-prey relationship, is maintained.

On the North American prairies, bison are able to enjoy the abundance of grass during the summer months. Winter, however, poses a great challenge to one herd in Yellowstone. Not only is do they have to endure temperatures of -40° Celsius, but their main food source is now buried a metre under snow. The herd works tirelessly using their massive neck muscles to shovel up to five tonnes of snow per day just to reach the withered grass below.

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During winter in Yellowstone, red foxes need to locate prey beneath a metre of snow. They pinpoint a target by listening carefully to sounds of movement below, before leaping into the air and diving headfirst into the snow. One individual spots an opportunity in the spaces where a bison herd has been digging for grass, and successfully hunts a vole in this way.

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Caribou females have travelled to the far north of Canada to calve in time for newly sprouting grass. Within days of being born, the calves will have to join their parents on the longest overland migration made by any animal so the first few days are crucial for building strength and testing their legs by running around. Once they set off, they are vulnerable to predation by Arctic wolves. One calf, just a few weeks old, manages to evade pursuit by a wolf; despite being slower at to speed, the calf's stamina allows it to outrun the predator and rejoin its hard.

Arctic wolves hunt migrating caribou in the far north of Canada. One wolf manages to separate a calf from its herd and begins pursuit on the tundra. Despite being faster over short stretches, the wolf lacks the stamina of the caribou calf and has to give up the chase.